From: Masami Ichikawa masami256@gmail.com
When trace_clock option is not set and unstable clcok detected, tracing_set_default_clock() sets trace_clock(ThinkPad A285 is one of case). In that case, if lockdown is in effect, null pointer dereference error happens in ring_buffer_set_clock().
Link: http://lkml.kernel.org/r/20200116131236.3866925-1-masami256@gmail.com
Cc: stable@vger.kernel.org Fixes: 17911ff38aa58 ("tracing: Add locked_down checks to the open calls of files created for tracefs") Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1788488 Signed-off-by: Masami Ichikawa masami256@gmail.com Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org --- kernel/trace/trace.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index ddb7e7f5fe8d..5b6ee4aadc26 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -9420,6 +9420,11 @@ __init static int tracing_set_default_clock(void) { /* sched_clock_stable() is determined in late_initcall */ if (!trace_boot_clock && !sched_clock_stable()) { + if (security_locked_down(LOCKDOWN_TRACEFS)) { + pr_warn("Can not set tracing clock due to lockdown\n"); + return -EPERM; + } + printk(KERN_WARNING "Unstable clock detected, switching default tracing clock to "global"\n" "If you want to keep using the local clock, then add:\n"